The present invention relates to a chuck device for holding tool bits to a drive shaft of a power tool or machine tool, and more particularly to a quick release chuck device incorporating a collet which is particularly useful in machining applications, such as routing, drilling, milling, and boring applications.
Conventional tool holding devices incorporate a body member or collet tool holder having a tapered collet that conforms to a hollow cone or recess defined in the body member. In certain applications, such as routers, the body member may comprise the end portion of the drive shaft and the hollow cone or recess may be defined in the end of the shaft. Typically, a threaded nut is provided having a conical cam surface which matches the conical surface of the outer forward collet face. During operation of this type of conventional device, the drive spindle or chuck of the machine tool must be held stationary in order to tighten the collet nut sufficiently. Flats are defined on the outer circumferential surface of the nut member so that a wrench can be engaged on the nut member to provide a sufficient tightening torque. For this reason, most router chucks and tool holders utilizing collets have spindle locks or are provided with extra wrenches for holding the drive shaft stationary and tightening the nut member onto the body member. Similarly, to release the tool, the machine shaft or chuck body must again be held stationary while the nut member is loosened with a wrench.
These known conventional devices have a number of drawbacks. For example, the tightening and loosening procedure has proven to be cumbersome and requires a separate device, such as a wrench, for locking the spindle shaft or for applying a tightening force to the nut member. Additionally, the degree of tightening of the nut member is limited by the frictional interface between the nut member and body member. Inconsistent nut tightening can create high stresses in the threads of the nut and tool holder causing damage in cases of overtightening.
Various attempts have been made in the art to provide improved chuck devices incorporating collets, particularly for high speed machine tools such as routers. U.S. Pat. No. 5,511,801 issued to Kanaan et al., for example, provides a significant improvement in the art. The '801 patent discloses an integrated collet and chuck device which is actuated by turning a sleeve relative to a body member, with the sleeve having a nut fixed therein. The nut engages a screw member which is rotatably concentric within the nut. Rotation of the nut drives the screw member in the longitudinal direction and the screw member engages a collet thereby causing the collet to grip on a tool shank.
The present invention provides an improvement to the state of the art of chuck devices utilizing collets.